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Graded Pitch

Graded Pitch

Graded Pitch

I've seen UNC threads described as "graded pitch" threads.  What is a graded pitch thread?

RE: Graded Pitch

OhioLarry:  The first thing that came to my mind is this might be a bungling of the term "constant-pitch series" threads, but I could be wrong.  Constant-pitch series threads, as the name implies, have a constant pitch for the threads on all bolts throughout that series, regardless of bolt diameter; and are normally available only in larger diameters, say 25 mm and above.

RE: Graded Pitch

The "grades" are in fact the "standard" pitch/diameter  series combination designations.  The "graded" pitches are Coarse ("UNC"), Fine ("UNF") and Extra Fine ("UNEF"), as opposed to the "constant" pitch series described by vonlueke, which are called out by the thread per inch numerical value and a "UN" callout, but without a "grade" (C, F or EF) designation.

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